1. Field of the Invention
The present invention relates to an apparatus and method for controlling multiple compressors (also called a multi-compressor) contained in an airconditioner, and more particularly to an apparatus and method for operating multiple compressors contained in an airconditioner, which stochastically operates or stops N compressors using a two-dimensional matrix, controls the N compressors to be equally operated without overlapping individual operation times of the N compressors, and alleviates fatigue of the compressors, such that the N compressors have longer lifetimes.
2. Description of the Related Art
Generally, airconditioners have been adapted to cool or heat a room using a cooling cycle of a refrigerant compressed at high temperature and high pressure.
The compressor includes a compressor having a compressor chamber for compressing a refrigerant, and a motor unit for varying the number of operating compressors. With the increasing demands of large-capacity airconditioners and multifunctional airconditioners, the above-mentioned compressor includes two or more multi-compressors, such that the airconditioner changes the number of operating compressors according to an indoor load condition, and at the same time operates the determined compressors.
FIG. 1 is a block diagram illustrating a conventional airconditioner having four compressors.
Referring to FIG. 1, the conventional airconditioner having four compressors includes: an indoor heat exchanger 11 which is arranged indoors, and cools/heats room air; an outdoor heat exchanger 12 which is arranged outdoors, and is heat-exchanged with outdoor air; a refrigerant conduit 17 for connecting the indoor heat exchanger 11 to the outdoor heat exchanger 12; first to fourth compressors 10, 20, 30, and 40; a common accumulator for accumulating a liquid refrigerant to control the first to fourth compressors 10, 20, 30, and 40 to receive only a gas refrigerant; a four-way valve which is connected to the first to fourth compressors 10, 20, 30, and 40, and switches a flow passage to transmit the refrigerant to one of the indoor and outdoor heat exchangers 11 and 12; and an expander 13 which is arranged between the indoor heat exchanger 11 and the outdoor heat exchanger 12, and expands the refrigerant passing through the indoor and outdoor heat exchangers 11 and 12 at low temperature and low pressure.
If the above-mentioned airconditioner having four compressors performs a cooling operation and has the highest indoor load, a controller operates all of the first to fourth compressors 10, 20, 30, and 40, transmits a high-temperature and high-pressure refrigerant generated from the first to fourth compressors 10, 20, 30, and 40 to the outdoor heat exchanger 12, controls the refrigerant received from the outdoor heat exchanger 12 to be heat-exchanged with outdoor air, condenses the high-temperature and high-pressure gas refrigerant into a liquid refrigerant, and transmits the liquid refrigerant to the expander 13. Upon receiving the liquid refrigerant, the expander 13 expands the received liquid refrigerant at low temperature and low pressure, and transmits the expanded refrigerant to the indoor heat exchanger 11. The indoor heat exchanger 11 absorbs peripheral heat of the received refrigerant, such that the refrigerant is evaporated. In the meantime, the refrigerant received from the indoor heat exchanger 11 is transmitted to the common accumulator 15 via the four-way valve, and circulates the first to fourth compressors 10, 20, 30, and 40, resulting in a cooling cycle.
In this case, if indoor load is lowered, the controller sequentially stops the fourth compressor 40, the third compressor 30, and the second compressor 20 from among the four compressors 10, 20, 30, and 40. Otherwise, if the amount of indoor load is increased, the controller sequentially drives the first compressor 10, the second compressor 20, the third compressor 30, and the fourth compressor 40.
Therefore, if the airconditioner performs a cooling operation and has the lowest indoor load, the controller operates only the first compressor 10 from among four compressors 10, 20, 30, and 40, and commands the refrigerant discharged from the first compressor 10 to circulate the outdoor heat exchanger 12, the expander 13, the indoor heat exchanger 11, and the first compressor 10, such that the indoor heat exchanger 11 can act as a cooler.
Otherwise, in the case of a heating operation, the controller allows the refrigerant to be counter-circulated in the above-mentioned cooling cycle.
However, if the conventional airconditioner including four compressors 10, 20, 30, and 40 has the highest load in response to indoor load, it operates all four compressors, such that the four compressors experience the same fatigue. Otherwise, if the conventional airconditioner operates only some compressors from among the four compressors, the fourth compressor 40 is not operated whereas the first compressor 10 is continuously operated, and the first to fourth compressors 10, 20, 30, and 40 have different operation times according to the degree of indoor load, such that eccentric fatigue may occur in one of the four compressors.
Also, some compressors are continuously operated, such that their lifetimes may be considerably shorter than those of the remaining compressors.